1. Field of the Invention
The present invention relates to a photo- and heat-sensitive recording material using a diazo compound and a coupler as color forming components. More specifically, the present invention relates to a photo- and heat-sensitive recording material which does not inhibit the fixing and which exhibits excellent color formation, color reproduction, and image durability. Further, the present invention relates to a magenta colorant which is produced from the foregoing material and which exhibits excellent absorption characteristics.
2. Description of the Related Art
A diazo compound is a compound having a very high chemical activity. Because of this chemical activity, a diazo compound easily forms an azo dye by reacting with a phenol derivative or a compound having an active methylene group, i.e., a so-called coupler. In addition, a diazo compound has a photosensitivity and loses its activity when irradiated with light.
Because of these properties, a diazo compound has been long utilized as a photosensitive recording material represented by diazo copy ("Fundamentals of Photographic Engineering--non-silver salt photography--" edited by the Photographic Society of Japan, 1982, pp.89-117, pp.182-201, published by Corona Publishing Co., Ltd.).
Further, by utilizing the property that a diazo compound is decomposed by light and loses its activity, recently it is also used in a recording material which requires the fixing of images. A typical example of this recording material proposed is a photo-fixing type heat sensitive recording material in which a diazo compound and a coupler are heated in accordance with an image signal so as to form an image by the reaction therebetween and the image thus formed is then fixed by the irradiation of light (for example, H. Sato et al., Journal of the Image Electronics Society of Japan, Vol. 11(1982), No. 4, pp.290-296).
These recording materials utilizing a diazo compound as an color forming element, however, has been associated with a drawback that the shelf life as a recording material is short, because the activity of the diazo compound is so high that the diazo compound undergoes a gradual thermal decomposition even in a dark place and the reactivity of the diazo compound is lost.
A variety of methods have been proposed to improve the instability of the diazo compound. One of the most effective means consists of the process wherein the diazo compound is enclosed in microcapsules.
Since such an encapsulation separates the diazo compound from a compound which accelerates the decomposition of the diazo compound, such as water and a base, the decomposition of the diazo compound is significantly inhibited. Therefore, the shelf life of the recording material using these microcapsules is remarkably improved (T. Usami et al., Journal of the Electrophotographic Society of Japan, Vol. 26(1987), No. 2, pp.115-125).
A generally adopted method for enclosing a diazo compound in microcapsules comprises the steps of dissolving a diazo compound in a hydrophobic solvent (oil phase), and adding the resulting solution into an aqueous solution (aqueous phase) containing a water-soluble polymer dissolved therein in order to emulsify the oil phase in the aqueous phase by means of, for example, a homogenizer, wherein a monomer or a prepolymer designed to form a wall of the microcapsule is added in advance either to the oil phase or to the aqueous phase, or alternatively to both phases so that a polymeric wall is formed by polymerization reaction or deposition of a polymer in the interface between the oil phase and the aqueous phase.
Details of these methods are described in, for example, A. Kondo, "Microcapsules" published by Nikkan Kogyo Shinbun Co., Ltd., 1970, and T. Kondo et al., "Microcapsules" published by Sankyo Publishing Co., Ltd., 1977.
Examples of the materials which can be used for the formation of the wall of the microcapsules include cross-linked gelatin, alginates, cellulosic materials, polyurea, polyurethane, melamine resins, nylon resins, and the like.
If the microcapsules are composed of a wall, such as a urea resin or a urethane resin, having a glass transition temperature which is slightly higher than room temperature, the capsule wall is impermeable to materials at room temperature but permeable to materials at a temperature above the glass transition temperature. Therefore, such microcapsules are called heat-responding microcapsules and are useful in a heat-sensitive recording material.
That is, a recording material comprising a substrate and a photo- and heat-sensitive recording layer formed thereon (the photo- and heat-sensitive recording layer comprises heat-responding microcapsules containing a diazo compound, a coupler, and a base), makes it possible to maintain the diazo compound for a long period of time in a stable state, to easily form a colored image by heating, and to fix the image by the irradiation of light.
This is because, as stated previously, the stability of the diazo compound can be remarkably improved by the encapsulation.
What is required to further improve these photo- and heat-sensitive recording materials includes the reduction of the inhibition of fixing and the improvement of color formation, color reproduction and image durability. For example, although Japanese Patent Application No. 9-152,414 proposes a coumarin derivative and a pyrazolone derivative as couplers to produce a magenta image, the invention described therein does not sufficiently meet the above-mentioned requirements and therefore improvement is needed.
On the other hand, although Japanese Patent Application Laid-Open (JP-A) No. 5-331,381 describes a pyrrolotriazole dye, the dye described therein does not have sufficient absorption characteristics and therefore improvement is still needed.